Basically, a synthesizer lacking a keyboard or any other built-in means for playing it. With today’s miniaturized electronics, it is possible to build a working synthesizer in a space much smaller than that required for a keyboard enclosure; by divorcing the synth electronics from the keyboard, the synth can be packaged in a much smaller form factor.Typically, an enclosure designed to be mounted in a standard 19” equipment rack is chosen, hence the name (A notable exception is the Oberheim Xpander, which is usually considered a "rackmount" synth even though it is physically too large to fit in a 19" rack.) Since the rackmount synth lacks a keyboard, it must be played by some external means; the problem is easily solved by a MIDI input allowing the synth to be played by another synth with a keyboard, a master keyboard, or a sequencer. Many synths today are sold in both keyboard and rackmount versions, and the rackmount nearly always costs several hundred dollars less, so the enterprising player who already has a good keyboard or other means of control can save money by buying additional synths as rackmounts.One disadvantage of the rackmount synth is that there is relatively little panel space for control knobs or switches, meaning that patch editing and control operations may have to be accomplished by either a user-unfriendly menu interface, or via some means of external control. See also tabletop.

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